This one is hard for me, I like music from all of those generations. Its a toss up between 2 and 3 for me so far.
Let's see, from '65-'76 I enjoy:
Queen
The Beatles (I actually preferred their later music)
Heart
Lynyrd Skynyrd
Aerosmith
Blue Öyster Cult
Led Zeppelin
Journey
Van Halen
Pink Floyd
AC/DC
Rolling Stones
The Doors
From '77 to mid 80's:
Michael Jackson
Prince
Stevie Nicks
Depeche Mode
Joan Jett
Guns n' Roses
Def Leppard
Phil Collins
The Scorpions
Ramones
Erasure
New Order
EDIT: Queen is the greatest rock band of all time. Challenged legitimatley only by Pink Floyd and The Beatles…imo.
Cannot agree more. They will always be my favorite. Freddie Mercury was the greatest and it breaks my heart forever that I have not seen them in concert when he was alive. I always feel like I was born a generation too late.
EDIT dues: It's funny I never think much of the 90's but when I look at it: The Pixies (as jerk pointed out) - Soundgarden - Stone Temple Pilots - Alice in Chains - were all very prominent and made some really great music. Even those that it has taken me forever to warm up to (Nirvana/Guns n Roses) made some great and memorable music. All these eras have a lot quality of when you look at them closely.
They are pretty much who I think of when I think of the 90's. The mid 90's had a lot of good music. I remember the first album I ever bought was Alanis Morrissette, I was around 10 years old. And this was also before they started labeling music with the "Parental Advisory" tags. Most of those bands I grew up listening to, aside from my love of the 80's as a kid, I appreciated most of the music from the 90's. Its strange, now that I'm older, I realize how much I love music from the 70's.